1. Field of the Invention
The present invention relates to gravity flow dryers for particulate material and, more particularly, to such a dryer having a drying column comprised of a removable module.
2. Description of the Prior Art
It is often necessary or desirable to dry freshly harvested grain before it is processed or stored. Storage of grain with excess moisture may cause quality deterioration and spoilage during subsequent storage.
The need to dry grain prior to storage has long been recognized in the art and many grain drying systems have been developed to accomplish this purpose. In many such prior systems, the grain is heated by air at a predetermined temperature during a first drying process and then the grain is quickly cooled to a desired storage temperature by exposing the grain to a flow of ambient air. One such system is the cross-flow column type grain dryer in which grain flows downwardly by gravity through a column having perforate walls and heated air is forced transversely through the perforate walls of the column to contact the grain to dry the grain or remove moisture. Typical of such cross-flow grain dryers are the grain dryers shown and described in U.S. Pat. No. 2,732,630 to Markowich and U.S. Pat. No. 3,238,640 to Fry.
The size of the perforations in the column walls in the typical prior art grain dryers has been set for the particular material to be dried. For example, if the dryer is to be used to dry corn, the perforations are somewhat smaller than the size of the corn. However, when drying smaller grains, such as rice, the perforations are smaller than when the dryer is designed for drying corn. Obviously, it is not feasible to dry small size grain in a dryer having large perforations in the walls defining the grain columns. Correspondingly, while it is possible to dry corn in a dryer having the small-sized perforations, as used in a rice or rope seed dryer, such drying is inefficient in that the air flow through the column is more restricted than desired. Thus, with the prior art dryers, it was necessary to have separate dryers for different types of grain or other particulate material to be dried. While some prior art dryers may have had perforate walls that were removed and replaced with walls having perforations of the same or a different size, such a conversion process was cumbersome and the dryers were not adapted to have removable modules for efficient and effective conversion involving a minimum of operator time and shut-down of the dryer. The present invention comprises a dryer having a removable module incorporating the columns, which can be quickly and conveniently removed and replaced to provide side walls having perforations appropriately sized for the material to be dried.